Method of producing a disposable protective cap for an infrared radiation thermometer

ABSTRACT

The art knows of methods of manufacturing disposable protective covers ( 1 ) that are seatable onto an infrared radiation thermometer suitable for introduction into a body cavity, in particular upon an ear canal temperature probe. To manufacture such a disposable protective cover ( 1 ) economically, a tubular body portion ( 2 ) is produced by extruding molten plastic following which the one end of the body portion ( 2 ) is closed with the window film ( 11 ).

This invention relates to a method of manufacturing a disposableprotective cover for an infrared radiation thermometer suitable forintroduction into a body cavity, in particular for an ear canaltemperature probe, in which a tubular body portion is formed of plasticmaterial, whose one end is open and whose opposite end is closed by awindow film that is transparent to infrared radiation.

Infrared radiation thermometers are widely used on persons for measuringtheir body temperature. Typically, such a radiation thermometer includesa housing with a window admitting radiation, internal optical componentsand an infrared sensor associated with an evaluation unit. The windowadmitting radiation closes off the interior of the housing of theradiation thermometer, thereby protecting the optical components and thesensor from contamination and destruction. As an additional protection,disposable protective covers of the type initially referred to areseated onto the forward end of the thermometer to protect the windowduring storage of the thermometer for one purpose, and to be exchangedfor reasons of hygiene for another purpose in cases where such athermometer is used by different persons.

Protective covers of the type initially referred to are described, forexample, in EP 0201 709 B1. The disposable speculum as described in thisprinted specification is fitted over the ear canal probe of a tympanicthermometer that is sensitive to infrared radiation. This disposablespeculum has a membrane made of polypropylene or polyethylene which istransparent to infrared radiation. The body portion carrying themembrane is an injection-molded part having the transparent membrane,which is manufactured as a thin film, thermally connected with the bodyportion's edge area bounding the window opening.

A further protective cover for a thermometer insertable into an earcanal is described in U.S. Pat. No. 5,293,862. To manufacture thisprotective cover, a tubular body portion is first formed by injectionmolding, and a membrane is attached to the one open end. For themanufacture of such a disposable protective cover, a mold is providedwhich has a cavity corresponding to the body portion. The mold isdesigned with separable parts in the region of the edge where the windowfilm is to be arranged, thus enabling a window film to be placed intothis parting plane prior to each injection molding operation. Injectionmolded onto the outside of the window film is an annular member arrangedin an extension of the wall of the body portion, so that upon completionof the injection molding operation the window film is retained betweenthe body portion and this outer ring.

On the basis of the prior art referred to in the foregoing and the knownmethods of manufacturing disposable protective covers for infraredradiation thermometers, it is an object of the present invention toprovide a method which enables such disposable protective covers to beproduced economically and which, in addition, offers a wide range ofvariation possibilities in respect of adapting the material to theproperties required from such a protective cover.

Based on a method of manufacturing a disposable protective cover of thetype initially referred to, this object is accomplished in that the bodyportion is produced by extruding molten plastic and subsequently closingthe one end of the body portion with the window film. The extrusionprocess enables the body portion to be manufactured economically.Further, it is possible to vary the length of the body portion inaccordance with the requirements, that is, extruded parts can be cut tothe desired length without any change to the extrusion device. Moreover,it is possible to profile the body portion which involves asleeve-shaped part, that is, reinforcement ribs or other axiallyextending projections or recesses, for example, can be injection-moldedonto the inside. Finally, another variation possibility is provided inthat the body portion can be extruded from different materials inrespect of its cross-section normal to its axis, for example, from afirmer material on the inside of the body portion, thereby providing asupport body engaging the measuring tip of a radiation thermometer, andfrom a softer material on its outside which conforms itself snugly tothe ear canal. After such a body portion is manufactured by extrusion,its one open end is closed with a window film which is transparent tothe relevant infrared measuring radiation.

As mentioned in the foregoing, according to claim 2 preferably theinside of the body portion, as seen in cross-section, that is, theradially inward region with which the disposable protective cover isseated onto the measuring end of the infrared radiation thermometer, isextruded from a firmer material, whereas the radially outward region isextruded from a softer material, with preferably the outward regionbeing extruded from a soft foamed material. Foamed materials suitablefor this purpose are polyethylene (PE), polypropylene (PP) orpolystyrene (PS). Such foamed materials should be provided with closedpores to prevent contaminants from depositing in the pores of the foamedmaterial not only during storage of these disposable protective covers,but also when they are being used.

The inward region of the protective cover or the body portion isextruded from the corresponding materials mentioned in the foregoingalso with respect to the foamed material, that is, from polyethylene(PE), polypropylene (PP) or polystyrene (PS). The hardness of thematerial is adjusted by suitable softeners. To impart a high stiffnessto the body portion while yet making it yielding so as to enable it tobe readily seated onto the measuring end of a radiation thermometer, inparticular also with a view to extruding such a protective cover in theform of a tubular body portion of approximately uniform diameter normalto its axis, it may be of advantage to profile the inward region of thetubular body portion. This profiling preferably takes the form ofaxially extending ribs. Such ribs then have their free longitudinaledges which extend towards the axis in engagement with the measuring endof the radiation thermometer. In cases where they are of acorrespondingly thin and flexible configuration, they may engage thecontour of the radiation thermometer also when this contour extendsconically. Further, a free space or air cushion is formed betweenadjacent ribs which imparts resilience and flexibility to the disposableprotective cover when, seated onto the forward end of a radiationthermometer, it is introduced into an ear canal. In particular incombination with a layer of foamed material on the outside of thedisposable protective cover as mentioned previously, a high usagecomfort can be accomplished with such a protective cover.

Moreover, the formation of profiles such as ribs on the one hand and theselection of different materials on the other hand, that is, a firmermaterial on the inside of the protective cover and a softer material onthe outside of the protective cover, enable a thermal decoupling to beaccomplished between the inside which fits over the thermometer and theoutside which engages the ear canal.

A variety of possibilities offer themselves to close off the one freeend of the extruded body portion with a window film. The window filmshould be relatively thin, that is, preferably of a thickness in therange of between 0.005 mm and 0.05 mm with polyethylene being thepreferred material for such a window film. To obtain very thin windowfilms, a process has proven to be advantageous in which the window filmis formed directly from molten plastic or a plastic solution. For thispurpose, the free end of the body portion which is to be closed isimmersed in such a solution so that a film is stretched over the edgesof the body portion, forming the window film following hardening.

Very good results are obtained if the molten plastic is comprised ofessentially low-molecular polyethylene with wax and oil additives.Low-molecular polyethylene can be set in a highly liquid state preciselyby the addition of wax and/or oils and by the action of heat.

As an alternative to molten plastic in the form of low-molecularpolyethylene, the molten plastic may be comprised of substantiallypolystyrene dissolved in a solvent as, for example, acetone.

As an alternative to the formation of a window film from molten plastic,it is possible to close the body portion by affixing a separate windowfilm. Suitably held in stretched fashion, such a window film can beadhered to the edge of the body portion by means of an adhesive.Preferably, however, the separate window film is secured to the forwardend of the body portion by welding or by exposure to ultrasound.

A further proven method of affixing the window film to the body portionis provided by laser beam application, preferably in the infrared range.Because the window film is invariably transparent to infrared radiation,laser radiation in the infrared range passes through the film, causingthe material of the body portion to melt. In addition, the use of colorpigments enables the plastic material of the body portion to be designedto be infrared absorbing. With this process, the window film is notdamaged as it is secured to the body portion. The formation of a uniformmelt beneath the film and thus good adhesion can be obtained. It is alsopossible to affix the film by means of the application of microwaveenergy when, in order to the generate the necessary heat in the area ofthe joint, humidity is introduced into this area or the edge is wettedwith water. Both laser radiation and microwaves can be adjusted todefined values in respect of the generation of heat and the penetrationof heat into the materials, so that only defined areas are heated forattachment of the window film.

Further details and the features of the method of the present inventionwill be described in more detail in the following with reference to theaccompanying drawings.

In the drawings,

FIG. 1 is a longitudinal sectional view of a disposable cover withextruded body portion according to the present invention, taken alongthe axis;

FIG. 2 is a sectional view of the cover of FIG. 1, taken along the lineII—II of FIG. 1;

FIG. 3A is a schematic longitudinal sectional view of the upper end of abody portion for a disposable protective cover having a separate windowfilm that is joined to the edge of the body portion by means ofultrasonic welding; and

FIG. 3B is a view of the forward end of the body portion of

FIG. 3A with the window film welded thereto.

A disposable protective cover 1 of the type illustrated in FIG. 2 insection includes a tubular or sleeve-shaped body portion 2 having itsupper free end 3 closed by an infrared window 4 formed of a thin filmthat is transparent to infrared radiation.

Such a disposable protective cover 1 is placed onto the measuring end ofan infrared radiation thermometer not illustrated in more detail, sothat the tip of the thermometer is received in the interior 5 of thedisposable protective cover 1. The clinical thermometer with itsprotective cover 1 seated in place is then introduced into a user's earcanal. Infrared radiation emitted from the tympanic membrane and fromthe ear canal enters the measuring end of the radiation thermometerthrough the window 4 and is directed to an infrared sensor inside theradiation thermometer. The temperature increase produced in the infraredsensor results in an electric output voltage from which the radiationtemperature is derived.

The protective cover 1 is a disposable part which, following temperaturemeasurement, is removed from the radiation thermometer to be replacedwith a new, unused protective cover 1 for taking another, for example,another person's temperature.

Because the protective cover 1 is utilized as a disposable part, economyof manufacture is essential, however with due consideration of the needfor the window 4 to possess the properties suitable for passage of theinfrared radiation to the infrared sensor of the associated radiationthermometer, which include adequate thinness on the one hand andtautness on the other hand, being held in stretched fashion on the upperfree end 3 of the sleeve-shaped molded body 2.

The body portion 2 is an extruded part of uniform diameter along itsaxis 6, as shown in FIGS. 1 and 2. During the process of extruding thebody portion 2, different materials are fed to the extruding nozzle inthe radially inward zone and in the radially outward zone, thus enablingthe material properties of the body portion 2 to be defined to satisfythe demands placed on such a protective cover. This means that theoutward region 7 is extruded from a softer, that is, foamed, material,whereas the radially inward region 8 is extruded from a firmer material.For the outward region 7, soft foamed materials made of polyethylene(PE), polypropylene (PP) or polystyrene (PS) are suitable. For theinward region 8, polyethylene (PE), polypropylene (PP) or polystyrene(PS) are equally employed with preference. The hardness degrees of thesematerials an be adjusted by appropriate softeners. Preferably, theoutward and inward regions 7, 8 are extruded from materials of likecharacter, that is, either from polyethylene, polypropylene orpolystyrene. Because the outward region 8 is foamed, the extruded bodyportion 2 yieldingly engages the ear canal in a manner pleasant for theuser of a thermometer equipped therewith.

To increase the stiffness of the body portion while yet providing itwith a defined flexibility, projections 9 extending in the direction ofthe axis 6 are extruded on the inside of the body portion, protrudingfrom the inner surface of the body portion by an amount of preferably 1to 3 mm, approximately. These projections 9 have -their free ends 10 inengagement with the outside of a radiation thermometer onto which thedisposable protective cover 1 is fitted.

Conventionally, the measuring tips of such radiation thermometers extendconically towards their end, so that it is precisely with theseprojections 9 or the areas of the body portion 2 lying between them thata high flexibility is obtained, while on the other hand a firmengagement of the disposable protective cover 1 with the measuring tipof a radiation thermometer is ensured. Such mated engagement of adisposable protective cover is customarily accomplished in that thedisposable protective cover 1 has in its interior 5 a shapecorresponding to the end of the radiation thermometer on to which thedisposable protective cover 1 is to be seated.

As FIG. 2 shows, a total of eight projections 9 are provided which areequidistantly spaced from each other in the interior 5 on thecircumference, that is, with reference to the axis 6 of the body portion2, adjacent projections 9 are arranged at a relative distance of 45°. Ifnecessary with a view to adjusting the flexibility of the disposableprotective cover, a number of projections 9 lower or higher than thenumber illustrated in FIG. 2 may be utilized, and in the latter case itis desirable that the projections be very thin, that is, of a laminarconfiguration, for maintaining adequate flexibility.

To obtain the window 4, a window film 11 illustrated in FIG. 3A as aseparate component is attached to the body portion 2. A preferred methodof securing the window film 11 to the free end 3 of the body portion 2is Ultrasonic welding. To this end, the window film 11 is deposited ontothe free end 3 of the body portion 2, and the ultrasonic head 12 isplaced onto the outside of the window film 11 which is urged against thefree end 3 of the body portion 2. Then the area of the joint, that is,the area of the free end, is exposed to ultrasonic energy from theultrasonic head 12, so that a defined amount of heat is produced forwelding or coalescence of the window film 11 with the free end 3 of thebody portion 2. As becomes apparent from FIG. 3A, the ultrasonic head 12is provided with a rounded contour, as a result of which welding of thewindow film 11 produces a chamfer 13 on the end of the body portion 2,thereby eliminating any sharp edges on the finished disposableprotective cover 1 which could be perceived as unpleasant when the userintroduces the radiation thermometer with the protective cover seatedthereon into an ear canal.

What is claimed is:
 1. A method of manufacturing a disposable protectivecover (1) for an infrared radiation thermometer suitable forintroduction into a body cavity, in particular for an ear canaltemperature probe, in which a tubular body portion (2) is formed ofplastic material, whose one end is open and whose opposite end is closedby a window film (11) that is transparent to infrared radiation,characterized in that the tubular body portion (2) has its radiallyoutward region (7), when seen in cross-section, extruded from a materialthat is softer than that of the radially inward region (8).
 2. Themethod as claimed in claim 1, characterized in that the outward region(7) is extruded from a soft foamed material.
 3. The method as claimed inclaim 2, characterized in that the soft foamed material is polyethylene(PE), polypropylene (PP) or polystyrene (PS).
 4. The method as claimedin claim 1, characterized in that the inward region (8) is extruded frompolyethylene (PE), polypropylene (PP) or polystyrene (PS).
 5. The methodas claimed in claim 1, characterized in that the radially inward region(8) of the tubular body portion (2) is profiled.
 6. The method asclaimed in claim 1 or 5, characterized in that axially extending ribs orprojections (9) are formed on the radially inward region (8) of thetubular body portion (2).
 7. The method as claimed in claim 1,characterized in that the window film (11) is formed by immersing theone end of the body portion (2) in molten plastic.
 8. The method asclaimed in claim 7, characterized in that the molten plastic isessentially comprised of low-molecular polyethylene with wax and oiladditives.
 9. The method as claimed in claim 7, characterized in thatthe molten plastic is essentially comprised of polystyrene dissolved ina solvent.
 10. The method as claimed in any one of the claims 7 to 9,characterized in that the window film (11) is formed with a thickness inthe range of between 0.005 mm and 0.05 mm.
 11. The method as claimed inclaim 1, characterized in that the one end of the body portion (2) isclosed by affixing a separate window film (11).
 12. The method asclaimed in claim 11, characterized in that the separate window film (11)is attached to the one end of the body portion (2) by adhesive bonding.13. The method as claimed in claim 11, characterized in that theseparate window film (11) is attached to the one end of the body portion(2) by welding.
 14. The method as claimed in claim 11 or 13,characterized in that the separate window film (11) is welded to the oneend of the body portion (2) by the application of ultrasound.
 15. Themethod as claimed in claim 11 or 13, characterized in that the separatewindow film (11) is welded to the one end of the body portion (2) by theapplication of a laser beam, preferably in the infrared range.
 16. Themethod as claimed in claim 11 or 13, characterized in that the separatewindow film (11) is welded to the one end of the body portion (2) by theapplication of microwaves.
 17. The method as claimed in claim 1,characterized in that the window film (11) is formed of polyethylene(PE) or polypropylene (PP).